Synthesis of functionalized high vinyl rubber

ABSTRACT

This invention is based upon the discovery that rubbery polymers having a high vinyl content and a low degree of branching can be synthesized with an initiator system that is comprised of (a) a lithium initiator selected from the group consisting of allylic lithium compounds and benzylic lithium compounds, (b) a Group I metal alkoxide, and (c) a polar modifier; wherein the molar ratio of the Group I metal alkoxide to the polar modifier is within the range of about 0.1:1 to about 10:1; and wherein the molar ratio of the Group I metal alkoxide to the lithium initiator is within the range of about 0.01:1 to about 20:1. These high vinyl polymers offer reduced levels of hysteresis and better functionalization efficiency. By virtue of their lower level of hysteresis these polymers can be utilized in manufacturing tire tread compounds that exhibit lower levels of rolling resistance and can accordingly be used to improve the fuel economy of motor vehicles without compromising other desirable characteristics, such as traction and tread-wear.

[0001] This patent application claims the benefit of U.S. ProvisionalPatent Application Serial No. 60/436,923, filed on Dec. 27, 2002.

BACKGROUND OF THE INVENTION

[0002] It is highly desirable for tires to exhibit good tractioncharacteristics on both dry and wet surfaces. However, it hastraditionally been very difficult to improve the tractioncharacteristics of a tire without compromising its rolling resistanceand tread wear. Low rolling resistance is important because good fueleconomy is virtually always an important consideration. Good tread wearis also an important consideration because it is generally the mostimportant factor that determines the life of the tire.

[0003] The traction, tread wear, and rolling resistance of a tire isdependent to a large extent on the dynamic viscoelastic properties ofthe elastomers utilized in making the tire tread. In order to reduce therolling resistance of a tire, rubbers having a high rebound havetraditionally been utilized in making the tire's tread. On the otherhand, in order to increase the wet skid resistance of a tire, rubberswhich undergo a large energy loss have generally been utilized in thetire's tread. In order to balance these two viscoelasticallyinconsistent properties, mixtures of various types of synthetic andnatural rubber are normally utilized in tire treads. For instancevarious mixtures of styrene-butadiene rubber and polybutadiene rubberare commonly used as a rubber material for automobile tire treads.However, such blends are not totally satisfactory for all purposes.

[0004] The inclusion of styrene-butadiene rubber (SBR) in tire treadformulations can significantly improve the traction characteristics oftires made therewith. However, styrene is a relatively expensive monomerand the inclusion of SBR is tire tread formulations leads to increasedcosts.

[0005] Carbon black is generally included in rubber compositions thatare employed in making tires and most other rubber articles. It isdesirable to attain the best possible dispersion of the carbon blackthroughout the rubber to attain optimized properties. It is also highlydesirable to improve the interaction between the carbon black and therubber. By improving the affinity of the rubber compound to the carbonblack, physical properties can be improved. Silica can also be includedin tire tread formulations to improve rolling resistance.

[0006] U.S. Pat. No. 4,843,120 discloses that tires having improvedperformance characteristics can be prepared by utilizing rubberypolymers having multiple glass transition temperatures as the treadrubber. These rubbery polymers having multiple glass transitiontemperatures exhibit a first glass transition temperature which iswithin the range of about −110° C. to −20° C. and exhibit a second glasstransition temperature which is within the range of about −50° C. to 0°C. According to U.S. Pat. No. 4,843,120, these polymers are made bypolymerizing at least one conjugated diolefin monomer in a firstreaction zone at a temperature and under conditions sufficient toproduce a first polymeric segment having a glass transition temperaturewhich is between −110° C. and −20° C. and subsequently continuing saidpolymerization in a second reaction zone at a temperature and underconditions sufficient to produce a second polymeric segment having aglass transition temperature which is between −20° C. and 20° C. Suchpolymerizations are normally catalyzed with an organolithium catalystand are normally carried out in an inert organic solvent.

[0007] U.S. Pat. No. 5,137,998 discloses a process for preparing arubbery terpolymer of styrene, isoprene, and butadiene having multipleglass transition temperatures and having an excellent combination ofproperties for use in making tire treads which comprises:terpolymerizing styrene, isoprene and 1,3-butadiene in an organicsolvent at a temperature of no more than about 40° C. in the presence of(a) at least one member selected from the group consisting oftripiperidino phosphine oxide and alkali metal alkoxides and (b) anorganolithium compound.

[0008] U.S. Pat. No. 5,047,483 discloses a pneumatic tire having anouter circumferential tread where said tread is a sulfur cured rubbercomposition comprised of, based on 100 parts by weight rubber (phr), (A)about 10 to about 90 parts by weight of a styrene, isoprene, butadieneterpolymer rubber (SIBR), and (B) about 70 to about 30 weight percent ofat least one of cis 1,4-polyisoprene rubber and cis 1,4-polybutadienerubber wherein said SIBR rubber is comprised of (1) about 10 to about 35weight percent bound styrene, (2) about 30 to about 50 weight percentbound isoprene and (3) about 30 to about 40 weight percent boundbutadiene and is characterized by having a single glass transitiontemperature (Tg) which is in the range of about −10° C. to about −40° C.and, further the said bound butadiene structure contains about 30 toabout 40 percent 1,2-vinyl units, the said bound isoprene structurecontains about 10 to about 30 percent 3,4-units, and the sum of thepercent 1,2-vinyl units of the bound butadiene and the percent 3,4-unitsof the bound isoprene is in the range of about 40 to about 70 percent.

[0009] U.S. Pat. No. 5,272,220 discloses a styrene-isoprene-butadienerubber which is particularly valuable for use in making truck tiretreads which exhibit improved rolling resistance and tread wearcharacteristics , said rubber being comprised of repeat units which arederived from about 5 weight percent to about 20 weight percent styrene,from about 7 weight percent to about 35 weight percent isoprene, andfrom about 55 weight percent to about 88 weight percent 1,3-butadiene,wherein the repeat units derived from styrene, isoprene and1,3-butadiene are in essentially random order, wherein from about 25% toabout 40% of the repeat units derived from the 1,3-butadiene are of thecis-microstructure, wherein from about 40% to about 60% of the repeatunits derived from the 1,3-butadiene are of the trans-microstructure,wherein from about 5% to about 25% of the repeat units derived from the1,3-butadiene are of the vinyl-microstructure, wherein from about 75% toabout 90% of the repeat units derived from the isoprene are of the1,4-microstructure, wherein from about 10% to about 25% of the repeatunits derived from the isoprene are of the 3,4-microstructure, whereinthe rubber has a glass transition temperature which is within the rangeof about −90° C. to about −70° C., wherein the rubber has a numberaverage molecular weight which is within the range of about 150,000 toabout 400,000, wherein the rubber has a weight average molecular weightof about 300,000 to about 800,000, and wherein the rubber has aninhomogeneity which is within the range of about 0.5 to about 1.5.

[0010] U.S. Pat. No. 5,239,009 reveals a process for preparing a rubberypolymer which comprises: (a) polymerizing a conjugated diene monomerwith a lithium initiator in the substantial absence of polar modifiersat a temperature which is within the range of about 5° C. to about 100°C. to produce a living polydiene segment having a number averagemolecular weight which is within the range of about 25,000 to about350,000; and (b) utilizing the living polydiene segment to initiate theterpolymerization of 1,3-butadiene, isoprene, and styrene, wherein theterpolymerization is conducted in the presence of at least one polarmodifier at a temperature which is within the range of about 5° C. toabout 70° C. to produce a final segment which is comprised of repeatunits which are derived from 1,3-butadiene, isoprene, and styrene,wherein the final segment has a number average molecular weight which iswithin the range of about 25,000 to about 350,000. The rubbery polymermade by this process is reported to be useful for improving the wet skidresistance and traction characteristics of tires without sacrificingtread wear or rolling resistance.

[0011] U.S. Pat. No. 5,061,765 discloses isoprene-butadiene copolymershaving high vinyl contents which can reportedly be employed in buildingtires which have improved traction, rolling resistance, and abrasionresistance. These high vinyl isoprene-butadiene rubbers are synthesizedby copolymerizing 1,3-butadiene monomer and isoprene monomer in anorganic solvent at a temperature which is within the range of about −10°C. to about 100° C. in the presence of a catalyst system which iscomprised of (a) an organoiron compound, (b) an organoaluminum compound,(c) a chelating aromatic amine, and (d) a protonic compound; wherein themolar ratio of the chelating amine to the organoiron compound is withinthe range of about 0.1:1 to about 1:1, wherein the molar ratio of theorganoaluminum compound to the organoiron compound is within the rangeof about 5:1 to about 200:1, and herein the molar ratio of the protoniccompound to the organoaluminum compound is within the range of about0.001:1 to about 0.2:1.

[0012] U.S. Pat. No. 5,405,927 discloses an isoprene-butadiene rubberwhich is particularly valuable for use in making truck tire treads, saidrubber being comprised of repeat units which are derived from about 20weight percent to about 50 weight percent isoprene and from about 50weight percent to about 80 weight percent 1,3-butadiene, wherein therepeat units derived from isoprene and 1,3-butadiene are in essentiallyrandom order, wherein from about 3% to about 10% of the repeat units insaid rubber are 1,2-polybutadiene units, wherein from about 50% to about70% of the repeat units in said rubber are 1,4-polybutadiene units,wherein from about 1% to about 4% of the repeat units in said rubber are3,4-polyisoprene units, wherein from about 25% to about 40% of therepeat units in the polymer are 1,4-polyisoprene units, wherein therubber has a glass transition temperature which is within the range ofabout −90° C. to about −75° C., and wherein the rubber has a Mooneyviscosity which is within the range of about 55 to about 140.

[0013] U.S. Pat. No. 5,654,384 discloses a process for preparing highvinyl polybutadiene rubber which comprises polymerizing 1,3-butadienemonomer with a lithium initiator at a temperature which is within therange of about 5° C. to about 100° C. in the presence of a sodiumalkoxide and a polar modifier, wherein the molar ratio of the sodiumalkoxide to the polar modifier is within the range of about 0.1:1 toabout 10:1; and wherein the molar ratio of the sodium alkoxide to thelithium initiator is within the range of about 0.05:1 to about 10:1. Byutilizing a combination of sodium alkoxide and a conventional polarmodifier, such as an amine or an ether, the rate of polymeriztioninitiated with organolithium compounds can be greatly increased with theglass transition temperature of the polymer produced also beingsubstantially increased. The rubbers synthesized using such catalystsystems also exhibit excellent traction properties when compounded intotire tread formulations. This is attributable to the uniquemacrostructure (random branching) of the rubbers made with such catalystsystems.

[0014] U.S. Pat. No. 5,620,939, U.S. Pat. No. 5,627,237, and U.S. Pat.No. 5,677,402 also disclose the use of sodium salts of saturatedaliphatic alcohols as modifiers for lithium initiated solutionpolymerizations. Sodium t-amylate is a preferred sodium alkoxide byvirtue of its exceptional solubility in non-polar aliphatic hydrocarbonsolvents, such as hexane, which are employed as the medium for suchsolution polymerizations. However, using sodium t-amylate as thepolymerization modifier in commercial operations where recycle isrequired can lead to certain problems. These problems arise due to thefact that sodium t-amylate reacts with water to form t-amyl alcoholduring steam stripping in the polymer finishing step. Since t-amylalcohol forms an azeotrope with hexane, it co-distills with hexane andthus contaminates the feed stream.

[0015] U.S. Pat. No. 6,140,434 discloses a solution to the problem ofrecycle stream contamination. U.S. Pat. No. 6,140,434 is based upon thediscovery that metal salts of cyclic alcohols are highly effectivemodifiers that do not co-distill with hexane or form compounds duringsteam stripping which co-distill with hexane. Since the boiling pointsof these metal salts of cyclic alcohols are very high, they do notco-distill with hexane and contaminate recycle streams. Additionally,metal salts of cyclic alcohols are considered to be environmentallysafe. In fact, sodium mentholate is used as a food additive.

[0016] U.S. Pat. No. 6,140,434 specifically discloses a process forpreparing a rubbery polymer having a high vinyl content which comprises:polymerizing at least one diene monomer with a lithium initiator at atemperature which is within the range of about 5° C. to about 100° C. inthe presence of a metal salt of a cyclic alcohol and a polar modifier,wherein the molar ratio of the metal salt of the cyclic alcohol to thepolar modifier is within the range of about 0.1:1 to about 10:1; andwherein the molar ratio of the metal salt of the cyclic alcohol to thelithium initiator is within the range of about 0.05:1 to about 10:1.

SUMMARY OF THE INVENTION

[0017] The present invention is based upon the discovery that rubberypolymers having a high vinyl content and a low degree of branching canbe synthesized with an initiator system that is comprised of (a) alithium initiator selected from the group consisting of allylic lithiumcompounds and benzylic lithium compounds, (b) a Group I metal alkoxide,and (c) a polar modifier; wherein the molar ratio of the Group I metalalkoxide to the polar modifier is within the range of about 0.1:1 toabout 10:1; and wherein the molar ratio of the Group I metal alkoxide tothe lithium initiator is within the range of about 0.01:1 to about 20:1.The key to the present invention is the use of an allylic lithiumcompound or a benzylic lithium compound in the initiator system.

[0018] These high vinyl polymers offer reduced levels of hysteresis andbetter functionalization efficiency. By virtue of their lower level ofhysteresis these polymers can be utilized in manufacturing tire treadcompounds that exhibit lower levels of rolling resistance and canaccordingly be used to improve the fuel economy of motor vehicleswithout compromising other desirable characteristics, such as tractionand tread-wear.

[0019] The subject invention further discloses a process for preparing arubbery polymer having a high vinyl content which comprises:polymerizing at least one diene monomer with a lithium initiatorselected from the group consisting of allylic lithium compounds andbenzylic lithium compounds at a temperature which is within the range ofabout 5° C. to about 120° C. in the presence of a Group I metal alkoxideand a polar modifier, wherein the molar ratio of the Group I metalalkoxide to the polar modifier is within the range of about 0.1:1 toabout 10:1; and wherein the molar ratio of the Group I metal alkoxide tothe lithium initiator is within the range of about 0.05:1 to about 10:1.

[0020] The present invention also reveals a process for preparing highvinyl polybutadiene rubber which comprises: polymerizing 1,3-butadienemonomer with a lithium initiator selected from the group consisting ofallylic lithium compounds and benzylic lithium compounds at atemperature which is within the range of about 5° C. to about 120° C. inthe presence of Group I metal alkoxide and a polar modifier, wherein themolar ratio of the Group I metal alkoxide to the polar modifier iswithin the range of about 0.1:1 to about 10:1; and wherein the molarratio of the Group I metal alkoxide to the lithium initiator is withinthe range of about 0.05:1 to about 10:1.

[0021] The subject invention further discloses a high vinyl polydienerubber which is comprised of at least 50 percent repeat units that areof vinyl microstructure based upon the total number of polydiene repeatunits in the rubbery polymer, wherein said high vinyl polybutadienerubber has a weight average molecular weight of at least 300,000,wherein said high vinyl polybutadiene rubber has a monomodalpolydispersity of at least 1.2, and a ratio of radius of gyration toweight average molecular weight of greater than 0.078 nm·mol/kg, whereinthe radius of gyration is determined at the weight average molecularweight by multi angle laser light scattering and wherein the weightaverage molecular weight is determined by multi angle laser lightscattering.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a plot of differential weight fraction versus molecularweight.

[0023]FIG. 2a is bar diagrams showing the weight percent of additionalmonomer grafted after the metallation step at a TMEDA/Li ratio of 3/1.

[0024]FIG. 2b is bar diagrams showing the weight percent of additionalmonomer grafted after the metallation step at a SMT/Li ratio of 0.1/1.

[0025]FIG. 2c is bar diagrams showing the weight percent of additionalmonomer grafted after the metallation step at a TMEDA/SMT/Li ratio of3/0.1/1.

[0026]FIG. 3 is a bar diagram showing the weight percent of additionalmonomer grafted at temperatures of 65° C., 72° C., and 78° C.

[0027]FIG. 4 is a plot of RMS radius versus molar mass.

[0028]FIG. 5 is a plot of G′ or G″ versus frequency.

[0029]FIG. 6 is a plot of tan delta versus frequency.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The rubbery polymers synthesized using the initiator systems ofthis invention can be made by the homopolymerization of a conjugateddiolefin monomer or by the copolymerization of a conjugated diolefinmonomer with a vinyl aromatic monomer. It is, of course, also possibleto make rubbery polymers by polymerizing a mixture of conjugateddiolefin monomers with one or more ethylenically unsaturated monomers,such as vinyl aromatic monomers. The conjugated diolefin monomers whichcan be utilized in the synthesis of rubbery polymers in accordance withthis invention generally contain from 4 to 12 carbon atoms. Thosecontaining from 4 to 8 carbon atoms are generally preferred forcommercial purposes. For similar reasons, 1,3-butadiene and isoprene arethe most commonly utilized conjugated diolefin monomers. Some additionalconjugated diolefin monomers that can be utilized include2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, and the like, alone or in admixture.

[0031] Some representative examples of ethylenically unsaturatedmonomers that can potentially be copolymerized into rubbery polymersusing the modifiers of this invention include alkyl acrylates, such asmethyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate andthe like; vinylidene monomers having one or more terminal CH₂═CH—groups; vinyl aromatics such as styrene, α-methylstyrene, bromostyrene,chlorostyrene, fluorostyrene and the like; α-olefins such as ethylene,propylene, 1-butene and the like; vinyl halides, such as vinylbromide,chloroethane (vinylchloride), vinylfluoride, vinyliodide,1,2-dibromoethene, 1,1-dichloroethene (vinylidene chloride),1,2-dichloroethene and the like; vinyl esters, such as vinyl acetate;α,β-olefinically unsaturated nitriles, such as acrylonitrile andmethacrylonitrile; α,β-olefinically unsaturated amides, such asacrylamide, N-methyl acrylamide, N,N-dimethylacrylamide, methacrylamideand the like.

[0032] Rubbery polymers which are copolymers of one or more dienemonomers with one or more other ethylenically unsaturated monomers willnormally contain from about 50 weight percent to about 99 weight percentconjugated diolefin monomers and from about 1 weight percent to about 50weight percent of the other ethylenically unsaturated monomers inaddition to the conjugated diolefin monomers. For example, copolymers ofconjugated diolefin monomers with vinylaromatic monomers, such asstyrene-butadiene rubbers which contain from 50 to 95 weight percentconjugated diolefin monomers and from 5 to 50 weight percentvinylaromatic monomers, are useful in many applications. The level ofthe vinylaromatic monomer is such copolymers with more typically bewithin the range of about 5 weight percent to about 40 weight percentand will more typically be within the range of about 15 weight percentto about 35 weight percent.

[0033] Vinyl aromatic monomers are probably the most important group ofethylenically unsaturated monomers that are commonly incorporated intopolydienes. Such vinyl aromatic monomers are, of course, selected so asto be copolymerizable with the conjugated diolefin monomers beingutilized. Generally, any vinyl aromatic monomer which is known topolymerize with organolithium initiators can be used. Such vinylaromatic monomers typically contain from 8 to 20 carbon atoms. Usually,the vinyl aromatic monomer will contain from 8 to 14 carbon atoms. Themost widely used vinyl aromatic monomer is styrene. Some examples ofvinyl aromatic monomers that can be utilized include styrene,1-vinylnaphthalene, 2-vinylnaphthalene, á-methylstyrene,4-phenylstyrene, 3-methylstyrene and the like.

[0034] In one embodiment of this invention a functionalized monomer iscopolymerized into the high vinyl polydiene rubber. The functionalizedmonomer will typically be incorporated into the high vinyl rubber in anamount which is within the range of 0.1 phm (parts by weight per 100parts by weight of monomer) to about 10 phm. The functionalized monomerwill more typically be incorporated into the polymer at a level with iswithin the range of about 0.2 phm to about 5 phm. The functionalizedmonomer will preferably be incorporated into the polymer at a level withis within the range of about 0.3 phm to about 3 phm.

[0035] The functionzlized monomers that can be copolymerized into suchhigh vinyl polydiene rubbers by utilizing the technique of thisinvention have a structural formula selected from the group consistingof

[0036] wherein R represents an alkyl group containing from 1 to about 10carbon atoms or a hydrogen atom, and wherein R¹ and R² can be the sameor different and represent hydrogen atoms or a moiety selected from thegroup consisting of

[0037] wherein R³ groups can be the same or different and represent amember selected from the group consisting of alkyl groups containingfrom 1 to about 10 carbon atoms, aryl groups, allyl groups, and alklyoxygroups having the structural formula —(CH₂)_(y)—O—(CH₂)_(z)—CH₃, whereiny represents an integer from 1 to 10, wherein z represents an integerfrom 1 to 10, wherein Z represents a nitrogen containing heterocycliccompound, wherein R⁴ represents a member selected from the groupconsisting of alkyl groups containing from 1 to about 10 carbon atoms,aryl groups, and allyl groups, and wherein x and represents an integerfrom 1 to about 10, and wherein n represents an integer from about 1 toabout 10, with the proviso that R1 and R2 can not both be hydrogenatoms;

[0038] wherein n represents an integer from 1 to about 10 and wherein mrepresents an integer from 1 to about 10, with the proviso that the sumof n and m is at least 4;

[0039] wherein n represents an integer from 1 to about 10, and wherein Rand R′ can be the same or different and represent alkyl groupscontaining from about 1 to about 10 carbon atoms;

[0040] wherein n represents an integer from 1 to about 10 and wherein mrepresents an integer from 4 to about 10;

[0041] wherein x represents an integer from about 1 to about 10, whereinn represents an integer from 1 to about 10 and wherein m represents aninteger from 1 to about 10, with the proviso that the sum of n and m isat least 4;

[0042] wherein R represents a hydrogen atom or an alkyl group containingfrom 1 to about 10 carbon atoms, wherein n represents an integer from 1to about 10, and wherein m represents an integer from 1 to about 10,with the proviso that the sum of n and m is at least 4; and

[0043] wherein n represents an integer from 0 to about 10, wherein mrepresents an integer from 1 to about 10, wherein x represents aninteger from 1 to about 10, and wherein y represents an integer from 1to about 10.

[0044] In functionalized monomers where R1 and/or R2 represent groups ofthe structural formula:

[0045] it is preferred for the R³ groups to represent hydrogen atoms oralkyl groups containing from 1 to 4 carbon atoms, and for x to representan integer from 1 to 4. In such functionalized monomers it is mostpreferred for the R³ groups to represent hydrogen atoms.

[0046] Such functionalized monomers can be synthesized by utilizing atechnique described in U.S. patent application Ser. No. 10/247,243,filed on Sep. 19, 2002. The teachings of U.S. patent application Ser.No. 10/247,243 are incorporated herein by reference. For instance,functionalized styrene monomer can be synthesized by reacting asecondary amine with vinyl benzyl halide, such as vinyl benzyl chloride,in the presence of a strong base to produce the functionalized styrenemonomer. This procedure can be depicted as follows:

[0047] This reaction is typically conducted at a temperature that iswithin the range of about −20° C. to about 40° C., and is preferablyconducted at a temperature which is within the range of about −10° C. toabout 30° C. This reaction will most preferable be conducted at atemperature which is within the range of about 0° C. to about 25° C. Thestrong base can be selected from a large variety of organic or inorganiccompounds. Examples of organic bases are aromatic and aliphatic amines,pyridines, such as triethylamine, aniline, and pyridine. Examples ofsuitable inorganic bases are the salts of weak mineral acids such hassodium carbonate, calcium carbonate, sodium hyrdroxide, calciumhydroxide, and aluminum hyrdoxide. After the reaction has been completedvolatile compounds are removed under reduced pressure yielding theproduct as a viscous residue.

[0048] Functionalized monomers that contain cyclic amines can also bemade by the same reaction scheme wherein a cyclic secondary amine isemployed in the first step of the reaction. This reaction scheme can bedepicted as follows:

[0049] The functionalized styrene monomers that can be used in thepractice of this invention are typically of the structural formula:

[0050] wherein R represents an alkyl group containing from 1 to about 10carbon atoms or a hydrogen atom, and wherein R¹ and R² can be the sameor different and represent hydrogen atoms or a moiety selected from thegroup consisting of

[0051] wherein R³ groups can be the same or different and represent amember selected from the group consisting of alkyl groups containingfrom 1 to about 10 carbon atoms, aryl groups, allyl groups, and alklyoxygroups having the structural formula —(CH₂)_(y)—O—(CH₂)_(z)—CH₃, whereiny represents an integer from 1 to 10, wherein z represents an integerfrom 1 to 10, wherein Z represents a nitrogen containing heterocycliccompound, wherein R⁴ represents a member selected from the groupconsisting of alkyl groups containing from 1 to about 10 carbon atoms,aryl groups, and allyl groups, and wherein x and represents an integerfrom 1 to about 10, and wherein n represents an integer from about 1 toabout 10, with the proviso that R¹ and R² can not both be hydrogenatoms. In these monomers R will typically represent a hydrogen atom or amethyl group, and x will typically represent an integer from 1 to 4. Inmost cases x will be 1. In one embodiment of this invention, R3 and R4can represent alkyl groups that contain from 1 to about 4 carbon atoms,aryl groups that contain from about 6 to about 18 carbon atoms, or allylgroups that contain from about 3 to about 18 carbon atoms.

[0052] Functionalized styrene monomers of the following structuralformulas:

[0053] wherein n represents an integer from 4 to about 10 are highlyuseful in the practice of this invention. In these functionalizedstyrene monomers n will normally represents 4 or 6.

[0054] The nitrogen containing heterocyclic group (Z group) willnormally be one of the following moieties:

[0055] wherein R⁵ groups can be the same or different and represent amember selected from the group consisting of alkyl groups containingfrom 1 to about 10 carbon atoms, aryl groups, allyl groups, and alkoxygroups, and wherein Y represents oxygen, sulfur, or a methylene group.

[0056] Some representative examples of rubbery polymers which can besynthesized in accordance with this invention include polybutadiene,polyisoprene, styrene-butadiene rubber (SBR), α-methylstyrene-butadienerubber, α-methylstyrene-isoprene rubber, styrene-isoprene-butadienerubber (SIBR), styrene-isoprene rubber (SIR), isoprene-butadiene rubber(IBR), á-methylstyrene-isoprene-butadiene rubber andα-methylstyrene-styrene-isoprene-butadiene rubber.

[0057] The polymerizations of this invention are normally carried out assolution polymerizations in an inert organic medium. However, theinitiator systems of this invention can also be utilized in bulkpolymerizations or vapor phase polymerizations. In any case, the vinylcontent of the rubbery polymer made is controlled by the amount ofmodifier present during the polymerization.

[0058] In solution polymerizations the inert organic medium which isutilized as the solvent will typically be a hydrocarbon which is liquidat ambient temperatures which can be one or more aromatic, paraffinic orcycloparaffinic compounds. These solvents will normally contain from 4to 10 carbon atoms per molecule and will be liquids under the conditionsof the polymerization. It is, of course, important for the solventselected to be inert. The term “inert” as used herein means that thesolvent does not interfere with the polymerization reaction or reactwith the polymers made thereby. Some representative examples of suitableorganic solvents include pentane, isooctane, cyclohexane, normal hexane,benzene, toluene, xylene, ethylbenzene and the like, alone or inadmixture. Saturated aliphatic solvents, such as cyclohexane and normalhexane, are most preferred.

[0059] The allylic lithium compounds that can be used are typically madeby reacting an alkyl lithium compound with a conjugated diolefinmonomer. The conjugated diolefin monomer will typically be 1,3-butadieneor isoprene. The benzylic lithium compounds that can be used aretypically made by reacting an alkyl lithium compound with a vinylaromatic monomer, such as styrene or alpha-methyl styrene. The alkyllithium compounds that can be used in making the allylic lithium orbenzylic lithium compound can be represented by the formula: R—Li,wherein R represents a hydrocarbyl radical containing from 1 to about 20carbon atoms. Some representative examples of alkyllithium compoundswhich can be employed include methyllithium, ethyllithium,isopropyllithium, n-butyllithium, sec-butyllithium, n-octyllithium,tert-octyllithium, n-decyllithium. Aryl lithium compounds, such as,phenyllithium, 1-napthyllithium, 4-butylphenyllithium, p-tolyllithium,1-naphthyllithium, 4-butylphenyllithium, p-tolyllithium,4-phenylbutyllithium, cyclohexyllithium, 4-butylcyclohexyllithium, and4-cyclohexylbutyllithium, can also be used. Some representative examplesof preferred alkyllithium compounds that can be utilized includeethylaluminum, isopropylaluminum, n-butyllithium,secondary-butyllithium, and normal-hexyllithium. Normal-butyllithium andsecondary-butyllithium are highly preferred lithium initiators.

[0060] The allylic lithium compound or the benzylic lithium compound canbe made by continuously adding the conjugated diolefin monomer or thevinyl aromatic monomer to a line containing a solution of the alkyllithium compound. In such cases, the line will typically flow into thereactor to initiate polymerization. In the alternative, the allyliclithium compound or the benzylic lithium compound can be made by a batchprocess wherein the conjugated diolefin monomer or vinyl aromaticmonomer is added into a solution containing the alkyl lithium compound.In either case, the molar ratio of the alkyl lithium compound to theconjugated diolefin monomer or vinyl aromatic monomer will be within therange of 1:1 to 1:50. The molar ratio of the alkyl lithium compound tothe conjugated diolefin monomer or vinyl aromatic monomer willpreferably be within the range of 1:2 to 1:25. The molar ratio of thealkyl lithium compound to the conjugated diolefin monomer or vinylaromatic monomer will more preferably be within the range of 1:5 to1:10.

[0061] The amount of lithium initiator utilized in the initiator systemsof this invention will vary with the specific allylic lithium orbenzylic lithium compound empolyed and with the molecular weight that isdesired for the rubber being synthesized. As a general rule in allanionic polymerizations, the molecular weight (Mooney viscosity) of thepolymer produced is inversely proportional to the amount of lithiumutilized. As a general rule, from about 0.01 phm (parts per hundredparts by weight of monomer) to 1 phm of the lithium catalyst will beemployed. In most cases, from 0.01 phm to 0.1 phm of the lithiumcatalyst will be employed with it being preferred to utilize 0.025 phmto 0.07 phm of the lithium catalyst.

[0062] Normally, from about 5 weight percent to about 35 weight percentof the monomer will be charged into the polymerization medium (basedupon the total weight of the polymerization medium including the organicsolvent and monomer). In most cases, it will be preferred for thepolymerization medium to contain from about 10 weight percent to about30 weight percent monomer. It is typically more preferred for thepolymerization medium to contain from about 20 weight percent to about25 weight percent monomer.

[0063] The polymerization temperature will normally be within the rangeof about 5° C. to about 120° C. For practical reasons and to attain thedesired microstructure the polymerization temperature will preferably bewithin the range of about 20° C. to about 80° C. Polymerizationtemperatures within the range of about 40° C. to about 70° C. are morepreferred with polymerization temperatures within the range of about 55°C. to about 65° C. being the very most preferred.

[0064] The polymerization is allowed to continue until essentially allof the monomer has been exhausted. In other words, the polymerization isallowed to run to completion. Since a lithium catalyst is employed topolymerize the monomer, a living polymer is produced. The living polymersynthesized will have a weight average molecular weight of at least300,000. The high vinyl polymer synthesized will typically have a weightaverage molecular weight that is within the range of about 350,000 toabout 2,000,000. The rubber synthesized will more typically have aweight average molecular weight that is within the range of about400,000 to about 1,000,000.

[0065] To increase the level of vinyl content the polymerization iscarried out in the presence of at least one polar modifier. Ethers andtertiary amines which act as Lewis bases are representative examples ofpolar modifiers that can be utilized. Some specific examples of typicalpolar modifiers include diethyl ether, di-n-propyl ether, diisopropylether, di-n-butyl ether, tetrahydrofuran, dioxane, ethylene glycoldimethyl ether, ethylene glycol diethyl ether, diethylene glycoldimethyl ether, diethylene glycol diethyl ether, triethylene glycoldimethyl ether, trimethylamine, triethylamine,N,N,N′,N′-tetramethylethylenediamine, N-methyl morpholine, N-ethylmorpholine, N-phenyl morpholine and the like.

[0066] The modifier can also be a 1,2,3-trialkoxybenzene or a1,2,4-trialkoxybenzene. Some representative examples of1,2,3-trialkoxybenzenes that can be used include1,2,3-trimethoxybenzene, 1,2,3-triethoxybenzene, 1,2,3-tributoxybenzene,1,2,3-trihexoxybenzene, 4,5,6-trimethyl-1,2,3-trimethoxybenzene,4,5,6-tri-n-pentyl-1,2,3-triethoxybenzene,5-methyl-1,2,3-trimethoxybenzene, and 5-propyl-1,2,3-trimethoxybenzene.Some representative examples of 1,2,4-trialkoxybenzenes that can be usedinclude 1,2,4-trimethoxybenzene, 1,2,4-triethoxybenzene,1,2,4-tributoxybenzene, 1,2,4-tripentoxybenzene,3,5,6-trimethyl-1,2,4-trimethoxybenzene,5-propyl-1,2,4-trimethoxybenzene, and3,5-dimethyl-1,2,4-trimethoxybenzene. Dipiperidinoethane,dipyrrolidinoethane, tetramethylethylene diamine, diethylene glycol,dimethyl ether and tetrahydrofuran are representative of highlypreferred modifiers. U.S. Pat. No. 4,022,959 describes the use of ethersand tertiary amines as polar modifiers in greater detail.

[0067] The utilization of 1,2,3-trialkoxybenzenes and1,2,4-trialkoxybenzenes as modifiers is described in greater detail inU.S. Pat. No. 4,696,986. The teachings of U.S. Pat. No. 4,022,959 andU.S. Pat. No. 4,696,986 are incorporated herein by reference in theirentirety. The microstructure of the repeat units which are derived frombutadiene monomer is a function of the polymerization temperature andthe amount of polar modifier present. For example, it is known thathigher temperatures result in lower vinyl contents (lower levels of1,2-microstructure). Accordingly, the polymerization temperature,quantity of modifier and specific modifier selected will be determinedwith the ultimate desired microstructure of the polybutadiene rubberbeing synthesized being kept in mind.

[0068] The Group I metal alkoxides that is used in the initiator systemof this invention will typically contain a Group I metal selected fromthe group consisting of lithium, sodium, potassium, rubidium, andcesium. The Group I metal alkoxide can be a compound of the formulaM—O—R, wherein M represents the Group I metal and wherein R representsan alkyl group containing from 1 to about 20 carbon atoms. U.S. Pat. No.5,654,384 and U.S. Pat. No. 5,906,956 disclose a number of sodiumalkoxide compounds that can be used in the practice of this invention.The teaching of U.S. Pat. No. 5,654,384 and U.S. Pat. No. 5,906,956 areincorporated herein by reference with respect to the types of sodiumalkoxide compounds that can be used.

[0069] The Group I metal alkoxide will preferably be a metal salt of thecyclic alcohol. Lithium, sodium, potassium, rubidium, and cesium saltsare representative examples of such salts with lithium, sodium, andpotassium salts being preferred. Sodium salts are typically the mostpreferred. The cyclic alcohol can be mono-cyclic, bi-cyclic ortri-cyclic and can be aliphatic or aromatic. They can be substitutedwith 1 to 5 hydrocarbon moieties and can also optionally containhetero-atoms. For instance, the metal salt of the cyclic alcohol can bea metal salt of a di-alkylated cyclohexanol, such as2-isopropyl-5-methylcyclohexanol or 2-t-butyl-5-methylcyclohexanol.These salts are preferred because they are soluble in hexane. Metalsalts of disubstituted cyclohexanol are highly preferred because theyare soluble in hexane and provide similar modification efficiencies tosodium t-amylate. Sodium mentholate is the most highly preferred metalsalt of a cyclic alcohol that can be empolyed in the practice of thisinvention. Metal salts of thymol can also be utilized. The metal salt ofthe cyclic alcohol can be prepared by reacting the cyclic alcoholdirectly with the metal or another metal source, such as sodium hydride,in an aliphatic or aromatic solvent.

[0070] The Group I metal alkoxide to the polar modifier will normally bewithin the range of about 0.1:1 to about 10:1 and the molar ratio ofGroup I metal alkoxide to the lithium initiator will normally be withinthe range of about 0.01:1 to about 20:1. It is generally preferred forthe molar ratio of the Group I metal alkoxide to the polar modifier tobe within the range of about 0.2:1 to about 5:1 and for the molar ratioof the Group I alkoxide to the lithium initiator to be within the rangeof about 0.05:1 to about 10:1. It is generally more preferred for themolar ratio of the Group I metal alkoxide to the polar modifier to bewithin the range of about 0.5:1 to about 1:1 and for the molar ratio ofthe Group I metal alkoxide to the lithium initiator to be within therange of about 0.2:1 to about 3:1.

[0071] After the polymerization has been completed, the living rubberypolymer can optionally be coupled with a suitable coupling agent, suchas a tin tetrahalide or a silicon tetrahalide. The rubbery polymer isthen recovered from the organic solvent. The polydiene rubber can berecovered from the organic solvent and residue by any means, such asdecantation, filtration, centrification and the like. It is oftendesirable to precipitate the rubbery polymer from the organic solvent bythe addition of lower alcohols containing from about 1 to about 4 carbonatoms to the polymer solution. Suitable lower alcohols for precipitationof the rubbery polymer from the polymer cement include methanol,ethanol, isopropyl alcohol, normal-propyl alcohol and t-butyl alcohol.The utilization of lower alcohols to precipitate the rubber from thepolymer cement also “kills” the living polymer by inactivating lithiumend groups. After the rubbery polymer is recovered from the solution,steam stripping can be employed to reduce the level of volatile organiccompounds in the polymer. The inert solvent and residual monomer canthen be recycled for subsequent polymerization.

[0072] There are valuable benefits associated with utilizing the highvinyl polydiene rubbers made with the initiator systems of thisinvention in tire tread compounds. These benefits include excellenttraction characteristics, low hysteresis and better functionalizationeffeciency. The high vinyl polydiene rubber will have at least 50percent repeat units that are of vinyl microstructure based upon thetotal number of polydiene repeat units in the rubbery polymer. The highvinyl polybutadiene rubber has a weight average molecular weight of atleast 300,000, wherein said high vinyl polybutadiene rubber has amonomodal polydispersity of at least 1.2, and a ratio of radius ofgyration to weight average molecular weight of greater than 0.078nm·mol/kg, wherein the radius of gyration is determined at the weightaverage molecular weight by multi angle laser light scattering andwherein the weight average molecular weight is determined by multi anglelaser light scattering.

[0073] The high vinyl polydiene rubber will preferably have a vinylcontent of at least 55 percent and a monomodal polydispersity of atleast 1.4. The high vinyl polydiene rubber will also preferable have aratio of radius of gyration to weight average molecular weight ofgreater than 0.08 nm·mol/kg. The high vinyl polydiene rubber will morepreferable have a ratio of radius of gyration to weight averagemolecular weight of greater than 0.082 nm·mol/kg.

[0074] It is, of course, possible to blend the high vinyl rubber withother rubbery polymers, such as natural rubber, synthetic polyisoprenerubber, cis-1,4-polybutadiene rubber, medium vinyl polybutadiene rubber,conventional solution styrene-butadiene rubber, emulsionstyrene-butadiene rubber, or conventional styrene-isoprene-butadienerubber, in making useful tire tread compounds.

[0075] The high vinyl polydiene rubber can be compounded utilizingconventional ingredients and standard techniques. For instance, thepolybutadiene rubber blends will typically be mixed with carbon blackand/or silica, sulfur, fillers, accelerators, oils, waxes, scorchinhibiting agents, and processing aids. In most cases, the high vinylpolydiene rubber blend will be compounded with sulfur and/or a sulfurcontaining compound, at least one filler, at least one accelerator, atleast one antidegradant, at least one processing oil, zinc oxide,optionally a tackifier resin, optionally a reinforcing resin, optionallyone or more fatty acids, optionally a peptizer and optionally one ormore scorch inhibiting agents. Such blends will normally contain fromabout 0.5 to 5 phr (parts per hundred parts of rubber by weight) ofsulfur and/or a sulfur containing compound with 1 phr to 2.5 phr beingpreferred. It may be desirable to utilize insoluble sulfur in caseswhere bloom is a problem.

[0076] Normally from 10 to 150 phr of at least one filler will beutilized in the blend with 30 to 80 phr being preferred. In most casesat least some carbon black will be utilized in the filler. The fillercan, of course, be comprised totally of carbon black. Silica can beincluded in the filler to improve tear resistance and heat build up.Clays and/or talc can be included in the filler to reduce cost. Theblend will also normally include from 0.1 to 2.5 phr of at least oneaccelerator with 0.2 to 1.5 phr being preferred. Antidegradants, such asantioxidants and antiozonants, will generally be included in the treadcompound blend in amounts ranging from 0.25 to 10 phr with amounts inthe range of 1 to 5 phr being preferred. Processing oils will generallybe included in the blend in amounts ranging from 2 to 100 phr withamounts ranging from 5 to 50 phr being preferred. The polybutadieneblends of this invention will also normally contain from 0.5 to 10 phrof zinc oxide with 1 to 5 phr being preferred. These blends canoptionally contain from 0 to 10 phr of tackifier resins, 0 to 10 phr ofreinforcing resins, 1 to 10 phr of fatty acids, 0 to 2.5 phr ofpeptizers, and 0 to 1 phr of scorch inhibiting agents.

[0077] In cases where silica is included in the tread rubber compound,the processing of the polydiene rubber blend is normally conducted inthe presence of a sulfur containing organosilicon compound to realizemaximum benefits. Examples of suitable sulfur containing organosiliconcompounds are of the formula:

Z—Alk—S_(n)—Alk—Z  (I)

[0078] in which Z is selected from the group consisting of

[0079] where R^(1 is an alkyl group of) 1 to 4 carbon atoms, cyclohexylor phenyl; wherein R^(2 is alkoxy of) 1 to 8 carbon atoms, orcycloalkoxy of 5 to 8 carbon atoms; and wherein Alk is a divalenthydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8.

[0080] Specific examples of sulfur containing organosilicon compoundswhich may be used in accordance with the present invention include:3,3′-bis(trimethoxysilylpropyl) disulfide,3,3′-bis(triethoxysilylpropyl) tetrasulfide,3,3′-bis(triethoxysilylpropyl) octasulfide,3,3′-bis(trimethoxysilylpropyl) tetrasulfide,2,2′-bis(triethoxysilylethyl) tetrasulfide,3,3′-bis(trimethoxysilylpropyl) trisulfide,3,3′-bis(triethoxysilylpropyl) trisulfide,3,3′-bis(tributoxysilylpropyl) disulfide,3,3′-bis(trimethoxysilylpropyl) hexasulfide,3,3′-bis(trimethoxysilylpropyl) octasulfide,3,3′-bis(trioctoxysilylpropyl) tetrasulfide,3,3′-bis(trihexoxysilylpropyl) disulfide,3,3′-bis(tri-2″-ethylhexoxysilylpropyl) trisulfide,3,3′-bis(triisooctoxysilylpropyl) tetrasulfide,3,3′-bis(tri-t-butoxysilylpropyl) disulfide, 2,2′-bis(methoxy diethoxysilyl ethyl) tetrasulfide, 2,2′-bis(tripropoxysilylethyl) pentasulfide,3,3′-bis(tricyclonexoxysilylpropyl) tetrasulfide,3,3′-bis(tricyclopentoxysilylpropyl) trisulfide,2,2′-bis(tri-2″-methylcyclohexoxysilylethyl) tetrasulfide,bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl3′-diethoxybutoxy-silylpropyltetrasulfide, 2,2′-bis(dimethylmethoxysilylethyl) disulfide, 2,2′-bis(dimethyl sec.butoxysilylethyl)trisulfide, 3,3′-bis(methyl butylethoxysilylpropyl) tetrasulfide,3,3′-bis(di t-butylmethoxysilylpropyl) tetrasulfide, 2,2′-bis(phenylmethyl methoxysilylethyl) trisulfide, 3,3′-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3′-bis(diphenylcyclohexoxysilylpropyl) disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl) tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl) trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3′-bis(ethyl di-sec.butoxysilylpropyl) disulfide, 3,3′-bis(propyl diethoxysilylpropyl)disulfide, 3,3′-bis(butyl dimethoxysilylpropyl) trisulfide,3,3′-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenylethoxybutoxysilyl 3′-trimethoxysilylpropyl tetrasulfide,4,4′-bis(trimethoxysilylbutyl) tetrasulfide,6,6′-bis(triethoxysilylhexyl) tetrasulfide,12,12′-bis(triisopropoxysilyl dodecyl) disulfide,18,18′-bis(trimethoxysilyloctadecyl) tetrasulfide,18,18′-bis(tripropoxysilyloctadecenyl) tetrasulfide,4,4′-bis(trimethoxysilyl-buten-2-yl) tetrasulfide,4,4′-bis(trimethoxysilylcyclohexylene) tetrasulfide,5,5′-bis(dimethoxymethylsilylpentyl) trisulfide,3,3′-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide,3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.

[0081] The preferred sulfur containing organosilicon compounds are the3,3′-bis(trimethoxy or triethoxy silylpropyl) sulfides. The mostpreferred compound is 3,3′-bis(triethoxysilylpropyl) tetrasulfide.Therefore as to formula I, preferably Z is

[0082] where R^(2 is an alkoxy of) 2 to 4 carbon atoms, with 2 carbonatoms being particularly preferred; Alk is a divalent hydrocarbon of 2to 4 carbon atoms with 3 carbon atoms being particularly preferred; andn is an integer of from 3 to 5 with 4 being particularly preferred.

[0083] The amount of the sulfur containing organosilicon compound offormula I in a rubber composition will vary depending on the level ofsilica that is used. Generally speaking, the amount of the compound offormula I will range from about 0.01 to about 1.0 parts by weight perpart by weight of the silica. Preferably, the amount will range fromabout 0.02 to about 0.4 parts by weight per part by weight of thesilica. More preferably the amount of the compound of formula I willrange from about 0.05 to about 0.25 parts by weight per part by weightof the silica.

[0084] In addition to the sulfur containing organosilicon, the rubbercomposition should contain a sufficient amount of silica, and carbonblack, if used, to contribute a reasonably high modulus and highresistance to tear. The silica filler may be added in amounts rangingfrom about 10 phr to about 250 phr. Preferably, the silica is present inan amount ranging from about 15 phr to about 80 phr. If carbon black isalso present, the amount of carbon black, if used, may vary. Generallyspeaking, the amount of carbon black will vary from about 5 phr to about80 phr. Preferably, the amount of carbon black will range from about 10phr to about 40 phr. It is to be appreciated that the silica coupler maybe used in conjunction with a carbon black, namely pre-mixed with acarbon black prior to addition to the rubber composition, and suchcarbon black is to be included in the aforesaid amount of carbon blackfor the rubber composition formulation. In any case, the total quantityof silica and carbon black will be at least about 30 phr. The combinedweight of the silica and carbon black, as hereinbefore referenced, maybe as low as about 30 phr, but is preferably from about 45 to about 130phr.

[0085] The commonly employed siliceous pigments used in rubbercompounding applications can be used as the silica. For instance thesilica can include pyrogenic and precipitated siliceous pigments(silica), although precipitate silicas are preferred. The siliceouspigments preferably employed in this invention are precipitated silicassuch as, for example, those obtained by the acidification of a solublesilicate, e.g., sodium silicate.

[0086] Such silicas might be characterized, for example, by having a BETsurface area, as measured using nitrogen gas, preferably in the range ofabout 40 to about 600, and more usually in a range of about 50 to about300 square meters per gram. The BET method of measuring surface area isdescribed in the Journal of the American Chemical Society, Volume 60,page 304 (1930).

[0087] The silica may also be typically characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, and more usually about 150 to about 300. The silica might beexpected to have an average ultimate particle size, for example, in therange of 0.01 to 0.05 micron as determined by the electron microscope,although the silica particles may be even smaller, or possibly larger,in size.

[0088] Various commercially available silicas may be considered for usein this invention such as, only for example herein, and withoutlimitation, silicas commercially available from PPG Industries under theHi-Sil trademark with designations 210, 243, etc; silicas available fromRhone-Poulenc, with, for example, designations of Z1165MP and Z165GR andsilicas available from Degussa AG with, for example, designations VN2and VN3.

[0089] Tire tread formulations which include silica and an organosiliconcompound will typically be mixed utilizing a thermomechanical mixingtechnique. The mixing of the tire tread rubber formulation can beaccomplished by methods known to those having skill in the rubber mixingart. For example the ingredients are typically mixed in at least twostages, namely at least one non-productive stage followed by aproductive mix stage. The final curatives including sulfur vulcanizingagents are typically mixed in the final stage which is conventionallycalled the “productive” mix stage in which the mixing typically occursat a temperature, or ultimate temperature, lower than the mixtemperature(s) than the preceding non-productive mix stage(s). Therubber, silica and sulfur containing organosilicon, and carbon black ifused, are mixed in one or more non-productive mix stages. The terms“non-productive” and “productive” mix stages are well known to thosehaving skill in the rubber mixing art. The sulfur vulcanizable rubbercomposition containing the sulfur containing organosilicon compound,vulcanizable rubber and generally at least part of the silica should besubjected to a thermomechanical mixing step. The thermomechanical mixingstep generally comprises a mechanical working in a mixer or extruder fora period of time suitable in order to produce a rubber temperaturebetween 140° C. and 190° C. The appropriate duration of thethermomechanical working varies as a function of the operatingconditions and the volume and nature of the components. For example, thethermomechanical working may be for a duration of time which is withinthe range of about 2 minutes to about 20 minutes. It will normally bepreferred for the rubber to reach a temperature which is within therange of about 145° C. to about 180° C. and to be maintained at saidtemperature for a period of time which is within the range of about 4minutes to about 12 minutes. It will normally be more preferred for therubber to reach a temperature which is within the range of about 155° C.to about 170° C. and to be maintained at said temperature for a periodof time which is within the range of about 5 minutes to about 10minutes.

[0090] Tire tread compounds made using such high vinyl polydiene rubberblends can be used in tire treads in conjunction with ordinary tiremanufacturing techniques. Tires are built utilizing standard procedureswith the high vinyl polydiene rubber blend simply being substituted forthe rubber compounds typically used as the tread rubber. After the tirehas been built with the high vinyl polydiene rubber containing blend, itcan be vulcanized using a normal tire cure cycle. Tires made inaccordance with this invention can be cured over a wide temperaturerange. However, it is generally preferred for the tires to be cured at atemperature ranging from about 132° C. (270° F.) to about 166° C. (330°F.). It is more typical for the tires of this invention to be cured at atemperature ranging from about 143° C. (290° F.) to about 154° C. (310°F.). It is generally preferred for the cure cycle used to vulcanize thetires to have a duration of about 10 to about 20 minutes with a curecycle of about 12 to about 18 minutes being most preferred.

[0091] This invention is illustrated by the following examples which aremerely for the purpose of illustration and are not to be regarded aslimiting the scope of the invention or the manner in which it can bepracticed. Unless specifically indicated otherwise, all parts andpercentages are given by weight.

EXAMPLES Materials and Methods

[0092] Materials.—Butadiene and styrene were supplied by The GoodyearTire & Rubber Company, and was freshly distilled and degassed withnitrogen prior to use. Hexane was supplied by Ashland Chemicals andpurified by passing over an activated bed of silica gel under a drynitrogen atmosphere. N-butyllithium (n-BuLi) was supplied by ChemetallInc. and was used as received. TMEDA was purchased from Aldrich and wasused as received. SMT was supplied by The Goodyear Tire & RubberCompany.

[0093] Polymerizations.—Batch polymerizations were conducted in a 3.8liter reactor. The reactor was equipped with a variable speed agitatorand a heating/cooling coil to control the reactor temperature via adistributed Foxboro control system. A representative procedure forconducting a polymerization was to first fill the reactor with hexaneand pickle with 1.5 ml of 1.6M n-BuLi solution at 65° C. The pickledhexane was then dumped from the reactor and the reactor was blown downwith dry nitrogen for two minutes to purge any residual liquid.Approximately 1500 grams of 15 weight percent styrene-butadiene (25/75weight percent) solution in hexanes was charged into the reactor. Thereactor temperature was then brought to its set point of 65° C., and apredetermined amount of modifier and n-BuLi was charged into the reactorusing a syringe via the injection port on the reactor. The reaction thencommenced and samples of the reaction mixture were taken via a diplegduring the course of polymerization for residual monomer analysisutilizing gas chromatography (GC). The GC results were used to calculatemonomer conversions in order to determine whether monomers reach theirfull conversions.

[0094] Characterization.—Size-exclusion chromatography (SEC) wasperformed using a Wyatt Technologies miniDawn light scattering detectorcoupled with a Hewlett Packard 1047A refractive index detector. PolymerLaboratories B, C, and D mixed microgel columns were utilized withtetrahydrofuran as the carrier solvent at a flow rate of 0.35 ml/min anda column temperature of 40° C. Sample preparation involved filtering a0.12 weight percent solution of polymer in THF through a 1.0 μm filterprior to injection. Polystyrene standards were used to calibrate theinstrument.

Results and Discussion

[0095] The initiation in anionic polymerization is always assumed to bea faster step compared to propagation, and the initiator n-BuLi wasimmediately consumed. Instant initiation may be assumed in batchpolymerization and in plug flow reactor processes. In a continuousprocess, the reactants and products constantly flow into and out of thereactor. Theoretically, every species exists in the reactor at any giventime due to the reactor residence time distribution. Therefore, in atypical butadiene-styrene copolymerization system, three reactivespecies, i.e. two propagating species of allylic lithium(butadienyllithium) and benzylic lithium (styryllithium) and initiatorn-BuLi may be present. In the presence of polar modifiers, these threereactive species may exhibit different metallation strengths. It is thusimportant to distinguish their individual metallation strength for anyprocess improvement aimed at reducing the polymer branching.

[0096] A. Preparation of Butadienyllithium and Styryllithium

[0097] To isolate the effects of different reactive species,butadienyllithium (allylic lithium) and styryllithium (benzylic lithium)species have to be prepared. Preformed butadienyllithium was preparedthrough the reaction of butadiene and n-butyllithium. In a 4-ozoven-dried nitrogen purged bottle, 50 grams of 15 weight percentbutadiene solution in hexanes was charged into the bottle. Using asyringe, 17.4 ml of 1.6M n-BuLi was added into the bottle to pre-form anallylic lithium initiator with the molar ratio of butadiene to n-BuLibeing 5:1. The bottle was placed in 65° C. water bath and tumbled for 30minutes.

[0098] Styryllithium cannot be prepared directly through the reaction ofn-butyllithium and styrene in hexane because oligomer of styrene willprecipitate from the hexane solution. A two-step procedure was thusdesigned in this study to form a soluble styryllithium. First butadieneoligomers were prepared by reacting butadiene with n-butyllithium asdescribed in the preparation of butadienyllithium. After the livingbutadienyl oligomer was preformed, a test polymerization was conductedto check the active concentration of butadienyllithium. Based upon theGPC result and the amount of butadiene from the test polymerization, theactive concentration was determined. A soluble form of benzylic lithiumwas then formed by adding 2 molar equivalents of styrene to the livingbutadienyl oligomers.

[0099] B. Metallation Method

[0100] Anionic systems using heavy alkali metal alkoxides have been aresearch topic for many years. The majority of studies were designed toidentify the resulting metallating species and to understand theoperating mechanism, while polymerization was neglected (see Modrini,A., Adv. Carbanion Chem., 1992, 1, 1; Lochmann, L.; Trekoval, J.Collect. Czech. Chem. Comm., 1988, 15, 585; Lochmann, L.; Lim, D., J.Organomet. Chem., 1971, 28, 153; and Pi, R.; Bauer, B.; Schade, C.;Schleyer, P. v. R., J. Organomet. Chem., 1986, 306, C1). In practice,the polymerization system is complicated by many factors such ascounter-cations and the addition of polar modifiers. In particular,multiple active lithium species are present in a copolymerization systemand in the polymerization process each reactive species may possessdifferent metallating strengths toward a polymer backbone. In addition,polymer chain propagation, metallation, and subsequent monomer additionoccur concurrently. It is thus essential to isolate these events toinvestigate the metallation mechanism of a single reactive species.

[0101] In U.S. Pat. No. 5,562,310, a procedure was described tometallate the polymer chain and prepare grafted copolymers. In thedisclosed method, it assumed that the additional n-BuLi was all consumedto metallate the terminated polymer backbone and additional monomer wasall grafted on the polymer backbones resulting in chain branching. Usinga similar approach, Kerns and Henning (see Kerns, M. L. and Henning, S.K., Presented at the Deutsche Kautschuk Tagung Meeting, September 2000)studied alkyllithium metallation with different counter-cations inbutadiene polymerization in the presence of TMEDA and sodium mentholate.They concluded that the mechanism of metallation reactions involve amulti-component complex.

[0102] In the current study, a similar three-step approach as used byKerns and Henning was adopted to investigate the metallation strength ofdifferent reactive species that are present in a continuouspolymerization process. First, a SBR rubber cement (i.e., base polymer)with 25 weight percent styrene was prepared. The molecular weight ofthis base polymer was targeted around 250,000 to 300,000 g/mol. Thismolecular weight is high enough to ensure a clean separation of thepolymer formed in subsequent reaction. Upon the completion of thereaction, a stoichiometric amount of ethanol was added into the reactorto terminate the living polymer chains. The second step was to metallatethe terminated polymer chains by adding a pre-determined amount ofco-modifiers and initiator with the ratios as described in Tables 1 and2. This reaction lasted about 45 minutes. Finally, an additional monomersolution (same as that used in the first step) was charged into thereactor to propagate the polymerization. The freshly charged monomer wasallowed to react until full conversion was achieved. The reaction wasthen terminated by injecting a small amount of ethanol and the finalpolymer was analyzed by SEC.

[0103] A typical SEC plot before and after the second monomer additionis shown in FIG. 1. The distribution with a single peak represents thebase polymer made in the first step. Final polymer shows a bimodaldistribution resulting from the mixture of polymers formed from thefirst step and the 3rd step. It is evident that a clean separation afterthe second monomer addition can be achieved.

[0104] The polymer chains formed after metallation were intentionallytargeted at a lower molecular weight than base polymer formed in thefirst step so that a clean separation based upon elution time on SEC canbe achieved. Thus, the amount of polymers associated with the differentorigins could be determined. That is, additional monomer added after themetallation step could be consumed only in two ways: one is to form newpolymer chains with lower molecular weight than the base polymer,another is to be grafted onto the base polymer chains that weremetallated. The amount of polymer associated with these two differentorigins can be estimated based upon the areas under the peaks. Bycomparing with the amount of monomers charged into the reactor fromthese two different steps, the amount of monomer grafted onto the basepolymer chains can be calculated. The metallation strength can becorrelated the amount of additional monomer grafted onto the basepolymers. If a larger amount of additional monomer was found to begrafted onto the base polymer, the initiator system exhibits strongermetallation power.

[0105] C. Metallation Strength of Alkyllithium, Allylic Lithium andBenzylic Lithium

[0106] Using the aforementioned metallation method, a set of experimentswas designed to study the metallation strength of n-BuLi,butadienyllithium, and styryllithium under the mixed modifier systemconsisting of TMEDA and sodium mentholate. The results were summarizedin Table I. Base polymer molecular weight and its polydispersity (1^(st)addition) are listed in the 3^(rd) and 4^(th) columns (labeled in thetable under the column headings). After the second monomer addition, themolecular weight and its distribution of base polymer were changed dueto the monomer grafted onto the backbone and their values are listed inthe 5^(th) and 6^(th) columns. Any newly formed polymer had much lowermolecular weight than the base polymer and its Mw and polydispersity aregiven in the 8^(th) and 9^(th) columns. The 7^(th) and 10^(th) columnsgive the estimated weight percentage of the polymers from the molecularweight distribution curves corresponding to the base polymer and newlyformed polymer, respectively. The theoretical weight fraction of newpolymer was calculated based upon the amount of monomer charged into thereactor and was listed in the 11^(th) column. This value is calculatedassuming no metallation occurred. The amount of monomer charged into thereactor after the metallation step that was then attached onto the basepolymer chains was calculated and listed in the last column(12^(th)).

[0107] To highlight the difference of metallation strength associatedwith the three initiators, the data in the last column in Table I wasre-grouped to reflect the different initiator systems in the metallationstep and was plotted in FIG. 2.

[0108] From the Table I and FIG. 2, it is observed that 1.) when allyliclithium and benzylic lithium initiators were used in the metallationstep, the monomer added after metallation was mostly consumed in theformation of new polymer chains, no matter what the modifiercombination; 2.) more than half of the additional monomer was grafted onthe base polymer when n-BuLi was used in the metallation step; and 3)the metallation strength of the initiator system is greatly enhancedeven with small amounts of sodium mentholate are present in the process(A-2). TABLE I BATCH METALLATION EXPERIMENTS 1^(st) addition Post 2^(nd)addition Base Polymer Base Polymer New polymer Theor. Mw Mw Amt Mw Amtamt Grafted* 2^(nd) addition (kg/mol) Mw/Mn (kg/mol) Mw/Mn (wt %)(kg/mol) Mw/Mn (wt %) (wt %) (wt %) Expt Ratio 3rd 4th 5th 6th 7th 8th9th 10th 11th 12th 2^(nd) addition initiator system: TMEDA/SMT/n-BuLiA-1 3.0/0.0/1.0 221.8 1.06 293.6 1.11 92.1 70.25 1.31 7.9 21.31 62.9 A-20.0/0.1/1.0 244.8 1.05 275.1 1.12 88.7 67.12 1.28 11.4 20.32 44.1 A-33.0/0.1/1.0 241.5 1.05 292.1 1.16 91.2 62.39 1.38 8.8 20.32 56.6 2^(nd)addition initiator system: TMEDA/SMT/Allylic lithium B-1 3.0/0.0/1.0244.8 1.05 257.2 1.05 90.4 34.33 1.38 9.65 9.43 −2.3 B-2 0.0/0.1/1.0232.0 1.05 235.3 1.05 71.9 21.95 1.23 28.1 26.5 −6.1 B-3 3.0/0.1/1.0309.0 1.07 314.8 1.12 91.0 65.2 1.01 8.97 9.35 4.0 2^(nd) additioninitiator system: TMEDA/SMT/Styryllithium C-1 3.0/0.0/1.0 345.3 1.02343.7 1.06 77.6 37.45 1.28 22.4 23.45 4.5 C-2 0.0/0.1/1.0 244.5 1.06250.3 1.06 79.2 25.87 1.15 20.8 20.94 0.7 C-3 3.0/0.1/1.0 239.6 1.05234.4 1.1 79.3 28.0 1.30 20.7 21.0 1.4

[0109] Earlier studies (see Falk, J. C.; Schlott, R. J.; Hoeg, D. F.;Pendleton, J. F. Rubber Chem. Tecnol.,, 1973, 46, 1044; and Tate, D. P.;Halasa, A. F.; Webb, F. J.; Koch, R. W.; Oberster, A. E. J. Polym.Sci.:Part A-1, 1971, 9, 139) demonstrated that the TMEDA/n-BuLi systemwould metallate diene-based polymers. However, a recent study by Kernsand Henning¹³ did not find that significant metallation occurred intheir system, albeit under different conditions. The current study (A-1)showed that substantial metallation did occur in this system with over60 wt % of the additional monomer being grafted onto the base polymerchains. Based upon these findings, it is concluded that the metallationstrength would follow the order of alkyllithium being stronger thanallylic lithium with is equivalent to benzylic lithium.

[0110] Although little metallation was found when allylic lithium andbenzylic lithium were used in the current study, our unpublished planttrial data show that branching increases from the first reactor to thesecond reactor when the modifier combination of TMEDA/SMT is used. Thisseems to be in contradiction to the concept and the above finding thatmetallation only occurs when alkyllithium is present in the reactor. Itis believed that there is no or very little free alkyllithium presenceafter the first reactor in a continuous process due to the rapidinitiation in a highly modified system. To resolve this, we investigatedthe effect of temperature on the extent of metallation using allyliclithium as an initiator. The results are summarized in Table II underthe same column format as explained for Table I. The data in the lastcolumn in Table II was plotted in FIG. 3. TABLE II TEMPERATURE EFFECT ONBATCH METALLATION 1^(st) addition Post 2^(nd) addition Base Polymer BasePolymer New polymer Theo. Metallation Mw Mw Amt Mw Amt amt Grafted* ExptTemp (° C.) (kg/mol) Mw/Mn (kg/mol) Mw/Mn (wt %) (kg/mol) Mw/Mn (wt %)(wt %) (wt %) 2^(nd) addition initiator system: TMEDA/SMT/allyliclithium = 3.0/0.1/1.0 B-3 65 309.0 1.07 314.8 1.12 91.03 65.2 1.01 8.979.35 4.0 D-2 72 260.0 1.04 263.2 1.12 80.2 33.49 1.34 19.8 22.62 12.5D-3 78 279.0 1.06 286.8 1.30 83.0 39.69 1.25 17.0 23.56 27.8

[0111] It is clear that the extent of metallation increases with thereaction temperature and the amount of monomer grafted onto the basepolymer monotonically increases. It is therefore not surprising that thedegree of branching will be higher after the first reactor in acontinuous process if higher temperatures are employed in the laterreactors

[0112] D. Practical Examples

[0113] To confirm the above finding, two continuous experiments weredesigned to prepare high vinyl SBRs using mixed modifiers of TMEDA andSMT (Table III). The continuous process contains two reactors. InExperiment 1, initiator n-BuLi was directly fed into the first reactor.Reactor temperatures in both reactors were kept at 85° C. As seen insubsection C, alkyllithium exhibits a much stronger metallation tendencythan allylic lithium or styryllithium. In Experiment 2, to eliminate thepossible existence of n-BuLi in the reactor, a preformed allylic lithiumwas prepared when n-BuLi (chain extended n-BuLi with butadiene) waspre-reacted with 10 butadiene units and the resulting oligomer was thenfed into the reactor. Reactor temperatures in both reactors weremaintained at 75° C. to minimize metallation and branching reactions.The characterization data of the polymers synthesized in these twoexperiments are summarized in Table III. TABLE III CHARACTERIZATION OFCONTINUOUS POLYMERS Sample Type Polymer a Polymer b Method to Pre-formedDirect Feed initiator Mooney (OE), 37.5 52.7 53.0 phr Gerstine Oil,ML₁₊₄, 100° C. Molecular Weight distribution Mn, g/mol 380,100 465,000Mw, g/mol 545,300 809,100 Polydispersity 1.44 1.74 Radius Gyration Rn,nm 40.3 45.4 Rw, nm 45.9 53.2 Branching level Rw/Mw, nm-mol/kg 0.08420.0658 M-DSC Tg (onset, OE), ° C. −28.8 −21.4

[0114] As described in the paper of Kerns and Henning, Size ExclusionChromatography (SEC) with Multi Angle Laser Light Scattering (MALLS) canbe used to determine the relative level of branching by comparing theradius of gyration at a given molar mass. Since branched polymerexhibits a smaller coil size compared to its linear counterpart, theradius gyration will be smaller at a given molecular weight (see Bauer,B. J.; Fetters, L. J., Rubber Chemistry and Technology, 1978, 51, 406).

[0115]FIG. 4 shows the root mean square radius as a function of molarmass for the high vinyl SBR samples. It is seen that both samples give asimilar radius at low molar masses. At higher weights, polymer b withn-BuLi being directly fed into the reactor has a much smaller radius athigh molecular weights, indicating a relatively higher branching levelin the polymer.

[0116] It is known that linear and branched polymers show differentlinear viscoelastic response under simple oscillatory shear flow.Branched polymers typically exhibit higher Newtonian viscosity at lowshear rates due to their increased relaxation time and entanglementscaused by the branching points. Dynamic testing with a constant stressparallel plate rheometer has been demonstrated to adequatelycharacterize the low shear rate behavior of polymers by extending thetest to low angular frequencies so that it allows the polymer sample toreach the plateau and terminal zone behavior (see Bauer, B. J.; Fetters,L. J., Rubber Chemistry and Technology, 1978, 51, 406).

[0117] Branched polymers normally show higher G′ values at low angularfrequencies because their increased physical entanglements confine themovement of polymer chains and the external deformation can betransferred into the elastic component of moduli. It was also found thatthe crossover frequency of elastic and loss shear modulus (G″ overtakesG′) correlates well with the level of branching given the samemicrostructure and molecular weight. FIG. 5 shows G′ and G″ behavior ofboth samples as a function of frequency. It is observed that there iscrossover for polymer a at the frequency of 0.4 rad/sec while nocrossover occurred for polymer b in the frequency range the measurementwas conducted. This implies that there are indeed more branching pointsalong the backbone of polymer a than there are in polymer b, even thoughboth polymers exhibit similar mooney viscosities. An alternative way toreflect the relative branching level is the dependency of tan delta(G″/G′) on frequency. The lower the value of tan delta, the morebranched polymer will be. FIG. 6 shows that the polymer a has muchhigher values of tan delta than that of polymer b. Moreover, polymer aexhibits crossover (tan Δ=1.0), while polymer b does not have. All ofthese means that polymer a have more linear macrostructure than polymerb. This is consistent with the analysis and results from theaforementioned metallation study

[0118] E. Compound Properties

[0119] A standard silica formation with 86 phr Rhodia Zeosil 1165 wasused with BR/sSBR at a 30/70 phr ratio. The BR used in the formulationwas Budene® 1207 high cis-polybutadiene rubber. The primary interest ofthis study is to demonstrate the benefit of in-situ initiatortechnology. The data from the compounding evaluation is summarized inTable IV. As aforementioned, the in-situ initiator technology willreduce the extent of metallation in our initiator system and thus leadto more linear polymer. When this polymer is used in a tread compoundformulation, it is expected to improve the hysteretic properties. It isevident from Table IV that the hot rebound is higher for polymer b andMetravib tan delta value at 50° C. is much lower than that of polymer a,even though polymer a has a slightly higher mooney viscosity. TABLE IVHYSTERETIC ANALYSIS OF HIGH VINYL SBRs Sample Type Polymer a Polymer bCompounded Money 40.1 42.8 Shore A 66.9 64.8 Goodyear-Healey ReboundCold Rebound (%) 8.8 8.6 Hot Rebound (%) 56.8 59.8 Metravib Tan d (50°C., 6%) 0.2679 0.2079 Tan d (−10° C., 1.5%) 0.819 0.838

[0120] A Metallation study using different initiators combined withmixed modifier of TMEDA and sodium mentholate has been conducted inbatch experiments. It is concluded that the metallation strength fordifferent initiators follows the order of alkyllithium being greaterthan allylic lithium which is equivalent to styryllithium. Reactiontemperature was also investigated with the selection of allylic lithiumand the combination of TMEDA and sodium mentholate as the modifiersystem. It was found that the metallation strength increasessignificantly with the temperature.

[0121] The results from the batch experiments were used to guide thedesign of an initiator feed system in a continuous process to minimizethe metallation tendency inherent to the highly modified reaction systemthat is necessary to produce polymer materials with high vinyl contentand high glass transition. The compounding evaluation demonstrated thatthe in-situ initiator technology does lead to lower branching level inthe polymer sample and thus the hysteretic properties in a silicaformulation were significantly improved.

[0122] Variations in the present invention are possible in light of thedescription of it provided herein. It is, therefore, to be understoodthat changes can be made in the particular embodiments described whichwill be within the full intended scope of the invention as defined bythe following appended claims.

What is claimed is:
 1. A process for preparing a rubbery polymer havinga high vinyl content which comprises: copolymerizing at least one dienemonomer and a functionalized monomer with a lithium initiator selectedfrom the group consisting of allylic lithium compounds and benzyliclithium compounds at a temperature which is within the range of about 5°C. to about 120° C. in the presence of a Group I metal alkoxide and apolar modifier, wherein the molar ratio of the Group I metal alkoxide tothe polar modifier is within the range of about 0.1:1 to about 10:1; andwherein the molar ratio of the Group I metal alkoxide to the lithiuminitiator is within the range of about 0.05:1 to about 10:1.
 2. A highvinyl polydiene rubber which is comprised repeat units that are derivedfrom at least one conjugated diene monomer and a functionalized monomer,wherein at least 50 percent of the repeat units are of vinylmicrostructure based upon the total number of polydiene repeat units inthe rubbery polymer, wherein said high vinyl polydiene rubber has aweight average molecular weight of at least 300,000, wherein said highvinyl polydiene rubber has a monomodal polydispersity of at least 1.2,and a ratio of radius of gyration to weight average molecular weight ofgreater than 0.078 nm·mol/kg, wherein the radius of gyration isdetermined at the weight average molecular weight by multi angle laserlight scattering and wherein the weight average molecular weight isdetermined by multi angle laser light scattering.
 3. A process asspecified in claim 1 wherein the functionalized monomer is of thestructural formula:

wherein R represents an alkyl group containing from 1 to about 10 carbonatoms or a hydrogen atom, and wherein R¹ and R² can be the same ordifferent and represent hydrogen atoms or a moiety of the structuralformula:

wherein x represents an integer from 1 to about 10, wherein n representsan integer from about 1 to about 10, and wherein R3 represents ahydrogen atom or an alkyl group containing from 1 to 4 carbon atoms,with the proviso that R¹ and R² can not both be hydrogen atoms.
 4. Aprocess as specified in claim 2 wherein R represents a hydrogen atom. 5.A process as specified in claim 2 wherein n represents 4 or
 6. 6. Aprocess as specified in claim 2 wherein x represents
 1. 7. A process asspecified in claim 2 wherein the conjugated diolefin monomer is1,3-butadiene.
 8. A process as specified in claim 2 wherein theconjugated diolefin monomer is isoprene.
 9. A process as specified inclaim 2 wherein the rubbery polymer is further comprised of repeat unitsthat are derived from a vinyl aromatic monomer.
 10. A process asspecified in claim 9 wherein the vinyl aromatic monomer is styrene. 11.A process as specified in claim 2 wherein the functionalized monomer ispresent in the rubbery polymer at a level which is within the range of0.1 to 10 parts by weight per 100 parts by weight of monomer.
 12. Aprocess as specified in claim 2 wherein the functionalized monomer is ofthe structural formula:

wherein n represents the integer
 4. 13. A rubbery polymer as specifiedin claim 2 wherein the functionalized monomer is of the structuralformula:

wherein n represents the integer
 6. 14. A process as specified in claim2 wherein said polar modifier is selected from the group consisting ofdiethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether,tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethyleneglycol diethyl ether, diethylene glycol dimethyl ether, diethyleneglycol diethyl ether, triethylene glycol dimethyl ether, trimethylamine,triethylamine, N,N,N′,N′-tetramethylethylenediamine, N-methylmorpholine, N-ethyl morpholine, N-phenyl morpholine, andalkyltetrahydrofurfuryl ethers.
 15. A process as specified in claim 1wherein the molar ratio of the Group I metal alkoxide to the polarmodifier is within the range of about 0.2:1 to about 5:1; and whereinthe molar ratio of the Group I metal alkoxide to the lithium initiatoris within the range of about 0.05:1 to about 10:1.
 16. A process asspecified in claim 15 wherein the polymerization is conducted at atemperature which is within the range of about 5° C. to about 120° C.17. A process as specified in claim 16 wherein the Group I metalalkoxide is a sodium salt of a cyclic alcohol.
 18. A process asspecified in claim 17 wherein the Group I metal alkoxide is sodiummentholate.
 19. A process as specified in claim 18 wherein the molarratio of the metal salt of the cyclic alcohol to the polar modifier iswithin the range of about 0.5:1 to about 1:1; and wherein the molarratio of the metal salt of the cyclic alcohol to the lithium initiatoris within the range of about 0.2:1 to about 3:1.
 20. A process asspecified in claim 19 wherein said polar modifier isN,N,N′,N′-tetramethyl ethylenediamine.
 21. A process as specified inclaim 18 wherein the polymerization is conducted at a temperature whichis within the range of about 20° C. to about 80° C.
 22. A process asspecified in claim 18 wherein the polymerization is conducted at atemperature which is within the range of about 40° C. to about 70° C.23. A process as specified in claim 2 wherein the lithium initiator isan allylic lithium compound.
 24. A process as specified in claim 2wherein the lithium initiator is a benzylic lithium compound.
 25. Aprocess as specified in claim 24 wherein said initiator system is voidof alkyl lithium compounds.
 26. A high vinyl polydiene rubber asspecified in claim 2 wherein the ratio of the radius of gyration toweight average molecular weight of the high vinyl polydiene rubber isgreater than 0.08 nm·mol/kg.
 27. A high vinyl polydiene rubber asspecified in claim 26 wherein the monomodal polydispersity of the highvinyl polydiene rubber is at least 1.3.
 28. A high vinyl polydienerubber as specified in claim 27 wherein the high vinyl polydiene rubberhas a weight average molecular weight that is within the range of about400,000 to about 1,000,000.
 29. A high vinyl polydiene rubber asspecified in claim 28 wherein the high vinyl polydiene rubber has anumber average molecular weight of at least 55 percent.
 30. A high vinylpolydiene rubber as specified in claim 29 wherein the ratio of theradius of gyration to weight average molecular weight of the high vinylpolydiene rubber is greater than 0.082 nm·mol/kg.
 31. A high vinylpolydiene rubber as specified in claim 30 wherein the monomodalpolydispersity of the high vinyl polydiene rubber is at least 1.4.
 32. Ahigh vinyl polydiene rubber as specified in claim 27 wherein the highvinyl polydiene rubber has a weight average molecular weight that iswithin the range of about 350,000 to about 2,000,000.
 33. A high vinylpolydiene rubber as specified in claim 29 wherein the polydiene repeatunits in the high vinyl polydiene rubber are derived from 1,3-butadieneand wherein the high vinyl polydiene rubber is high vinyl polybutadienerubber.
 34. A high vinyl polydiene rubber as specified in claim 29wherein the polydiene repeat units in the high vinyl polydiene rubberare derived from isoprene and wherein the high vinyl polydiene rubber is3,4-polyisoprene rubber.
 35. A high vinyl polydiene rubber as specifiedin claim 33 wherein the repeat units in the high vinyl rubber arefurther derived from a vinyl aromatic monomer.
 36. A high vinylpolydiene rubber as specified in claim 35 wherein the vinyl aromaticmonomer is styrene and wherein the high vinyl polydiene rubber isstyrene-butadiene rubber.